Solar Collector Costs, Efficiencies, and Suppliers

Swimming pool and rooftop water heaters can convert solar energy into heat with an efficiency of 50-70%. The efficiencies of electricity-generating solar collector systems are much lower. They operate at efficiencies from 5% to about 30%. 

Thin-film solar shingles used on residential roofs today are only about 5 to 8% efficient. The efficiency of solar towers is also about 5%. Photovoltaic (PV) cell efficiencies range from about 5% for amorphous silicon (A-Si) designs, 9% to 10% for CdTe modules, and 13% to 16% for crystalline silicon modules. SEGS efficiencies are between 10 and 25%. 

Fresnel lens-type PV concentrators have operated at 26% efficiency (Amonix, Inc.). The efficiency of concentrating PV designs can reach 25-30%, and DSG thermal systems can also reach 30%. Similarly, the efficiency of dish concentrators using Stirling heat engines is also about 30%. Table 1.42 provides a summary of solar collector costs, efficiencies, and suppliers. 

experimental PV design by Spectrolab using concentrated sunlight has reached an efficiency of 40%. This milestone achievement was verified by the DOE s National Renewable Energy Laboratory (NREL) in Golden, Colorado. 

The average cost of solar electricity in the United States is about 12 J/ kWh. The wholesale costs of 1 kWh of electricity in 2007 in the United States (according to the New York Times, July 11, 2007) are as follows pulverized coal—5.7 t, nuclear—6.4tf, coal gas—6.6 t, natural gas—72 t, wind—9.6tf, and biomass—10.7tf. 

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